diff --git a/test/Dockerfile b/test/Dockerfile
index df19f46..a359aae 100644
--- a/test/Dockerfile
+++ b/test/Dockerfile
@@ -2,6 +2,8 @@ ARG from
 
 FROM $from
 
+ENV BUNDLE_GEMFILE=/gem/Gemfile
+
 WORKDIR /gem
 
 CMD ["sh", "-xc", "bin/setup && appraisal install && appraisal rake test"]